The damaging effects of wind gusts in wind turbines are well known in the art. If the wind speed increases in a small interval of time the generator speed may exceed its allowed limits because the WT controller is not able to generate a fast enough reaction, and this can cause potential damaging effects for the generator and other wind turbine components.
In the case of an extreme operating gust which also produces extreme loads on main structural components such as the blade root and the tower bottom a typical solution is shutting down the wind turbine. In this respect WO 2004/077068 describes the use of lidar means for detecting gusts well before the wind change reaches the turbine tower so that the blades could be feathered using the pitch control means.
A known approach for coping with wind gusts is using the generator torque control means for avoiding over-speed problems. However this technique involves risks of causing huge loads in several wind turbine components.
Another approach disclosed for example in U.S. Pat. No. 7,342,323 is based in sensing the wind speed at a desired distance from the wind turbine generator and controlling the pitch of the blades of the wind turbine using said “advanced” information of the wind speed. However the complexity and the lack of robustness of this technique raise reliability problems.
WO 2007/138138 in the name of the applicant discloses a solution for an extreme operating gust that keeps the wind turbine in operation and minimizes the bending moments carrying out a sudden increase of the pitch angle by saturating the minimum pitch rate value when the extreme operating gust is detected. This technique is applicable to a very particular case of wind gust.
The present invention focuses on finding a solution for these drawbacks.